R commands - rslides - Learning R Patrick Lam setting up I...

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Unformatted text preview: Learning R Patrick Lam setting up I download R from CRAN I work in the console (code not saved) I open a script, type code in script, and save as a .R file Example code is in red R as calculator > 5 + 4 [1] 9 > 8 * 2 - sqrt(9) [1] 13 > log(4)/9^2 [1] 0.01711 objects R is an object-oriented programming language. Use <- as assignment operator for objects. > 5 + 4 [1] 9 > my.sum <- 5 + 4 > my.sum [1] 9 > my.name <- "Patrick" > my.name [1] "Patrick" vectors All objects consist of one or more vectors . vector: a combination of elements (i.e. numbers, words), usually created using c() , seq() , or rep() > empty.vector <- c() > empty.vector NULL > one.to.five <- c(1, 2, 3, 4, 5) > one.to.five [1] 1 2 3 4 5 > poli.sci <- c("theory", "amer.", "comp.", "ir") > poli.sci [1] "theory" "amer." "comp." "ir" > one.to.ten <- 1:10 > one.to.ten [1] 1 2 3 4 5 6 7 8 9 10 > two.to.five <- seq(from = 2, to = 5, by = 1) > two.to.five [1] 2 3 4 5 > all.fours <- rep(4, times = 5) > all.fours [1] 4 4 4 4 4 All elements in a vector must be of the same data type! data types I numeric I character I logical numeric: numbers > three <- 3 > three [1] 3 > is.numeric(three) [1] TRUE > as.numeric("3") [1] 3 character: for example, words or phrases (must be in ””) > president <- "Barack Obama" > president [1] "Barack Obama" > is.character(president) [1] TRUE > as.character(3) [1] "3" logical: TRUE (T) or FALSE (F) > num.vec <- c(5, 6, 4) > logical.vec <- num.vec == 6 > logical.vec [1] FALSE TRUE FALSE > is.logical(logical.vec) [1] TRUE can also be represented as numeric 1 or 0: > as.numeric(logical.vec) [1] 0 1 0 All elements in a vector must be of the same data type! I if a vector has a character element, all elements become character > mixed.vec <- c(5, "Patrick", TRUE) > mixed.vec [1] "5" "Patrick" "TRUE" I if a vector has both numeric and logical elements, all elements become numeric > mixed.vec2 <- c(10, FALSE) > mixed.vec2 [1] 10 character > numeric > logical object classes All objects consist of one or more vectors. In addition to vector, objects can be of one of the following classes: I matrix I array I dataframe I list matrix A matrix is a two-dimensional ( r × c ) object (think a bunch of stacked or side-by-side vectors). > a.matrix <- matrix(c(1, 2, 3, 4), nrow = 2, ncol = 2) > a.matrix [,1] [,2] [1,] 1 3 [2,] 2 4 > class(a.matrix) [1] "matrix" All elements in a matrix must be of the same data type. character > numeric > logical array An array is a three-dimensional ( r × c × h ) object (think a bunch of stacked r × c matrices). All elements in an array must be of the same data type (character > numeric > logical). > an.array <- array(0, dim = c(2, 2, 3)) > an.array , , 1 [,1] [,2] [1,] [2,] , , 2 [,1] [,2] [1,] [2,] , , 3 [,1] [,2] [1,] [2,] dataframe A dataframe is a two-dimensional ( r × c × h ) object (like a matrix)....
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R commands - rslides - Learning R Patrick Lam setting up I...

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